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H-001-1/2021: Pearl Harbor, 7 December 1941

Dec. 23, 2021 | By NHHC Director Samuel Cox
(This is a revised and updated version of H-Gram 001/H-001-1 from 2016)
The following is not intended to be a comprehensive account of the Pearl Harbor attack, nor to whitewash the numerous errors of judgment and failures of process that occurred on all levels of the U.S. chain of command from the President to the tactical level. Over time, the lessons of history tend to get distilled to a “bumper sticker” level, when the reality is far more complex and nuanced . . . and many times the conventional-wisdom bumper sticker is just plain wrong.
There is no question that the United States and the Navy were not prepared for war, despite the fact that Navy leaders well understood that U.S. diplomacy and economic embargos were pushing the Japanese toward initiating hostilities. Navy leaders kept arguing for U.S. diplomats to back off in order to buy more time. The commanders at Pearl Harbor were anticipating war far more than they were ever given credit for. Hopefully, this will stimulate you and your sailors to want to know more.
Things You Might Not Have Heard About Pearl Harbor
Vice Admiral Nagumo’s (commander of the Japanese Carrier Strike Force, the Kido Butai) post-attack report stated that after the first five minutes U.S. antiaircraft fire became so intense that it effectively negated the effect of surprise. The fact that more Japanese planes weren’t shot down (9 on the first wave, 20 on the second wave) had more to do with the ineffectiveness of the weapons being used than due to surprise. The .50-caliber machine guns had too short a range, the number of jam-prone 1.1-inch quad antiaircraft guns was insufficient, and the 5-inch guns couldn’t elevate enough to counter dive-bombers. There were also large numbers of dud rounds. The number of Japanese aircraft lost is always cited in accounts (to demonstrate the lopsided nature of the battle). Less commonly cited is that 111 additional aircraft of the total of 350 were hit by antiaircraft fire, but were not brought down, although over 20 of the damaged aircraft that returned to the carriers were dumped over the side. This also points to the inadequacy of the weapons more than the readiness and training of U.S. gunners.
Japanese sources reported astonishment at the volume of fire put up by U.S. ships at Pearl Harbor, and the increasing intensity and accuracy were a major factor in Nagumo’s decision not to send a third wave (although there were many other factors as well). The U.S. shipboard 5-inch guns, which became active mostly after the first sections of torpedo bombers had already dropped their weapons, fired over 3,100 rounds, which actually accounted for the majority of U.S. civilian deaths (all the damage in Honolulu was from U.S. antiaircraft shell fragments returning to earth).
The deficiencies of antiaircraft guns were well known to Navy leaders in Washington, demonstrated in exercises at sea, but were uncorrected until late 1942 with the introduction of Bofors 40-mm, Oerlikon 20-mm, and 5-inch shells with proximity fuses. Due to the pre-war budget-driven paucity of live-fire training, the large number of defective rounds came as a very unpleasant surprise to the defenders at Pearl Harbor. The Japanese torpedo planes that attacked Battleship Row (all in the first wave) also rolled in five minutes before planned, and even so, five of the last nine were shot down; had they been on schedule, their losses to U.S. antiaircraft fire would have been even greater.
The known antiaircraft deficiency of the U.S. ships (based on exercise experience) was a principle factor in why the battleships were in port rather than at sea (“Sunday” had little to do with it). The two U.S. carriers (Lexington [CV-2] and Enterprise [CV-6]) in the mid-Pacific were away on higher-priority national tasking to deliver U.S. Marine aircraft (stripped from Pearl Harbor defenses) to Midway and Wake Island. These were to support the transit of B-17 bombers to the Philippines in a hastily conceived change of national strategy to use bombers to deter a Japanese attack against the Philippines. The original orders called for the carriers to carry and launch U.S. Army Air Forces fighters (also stripped from Hawaii), but Admiral Kimmel succeeded in convincing Washington otherwise. Without carrier air cover, the battleships at sea were considered to be highly vulnerable to both air and submarine attack, and the lack of carrier air cover was the principle reason Kimmel brought the fleet in. In the event the ships were sunk, they wouldn’t be lost in deep water with most of their crews.
In Pearl Harbor, the responsibility for air defense was with the Army (the Navy was responsible for long-range reconnaissance). The Army’s capability to defend Pearl Harbor against air attack was a known serious deficiency, one that the Army commander in Hawaii, Lieutenant General Short, had lobbied hard to correct. However, he had been overridden by Washington due to higher priority elsewhere. Despite knowing this, Kimmel reasoned that having the ships in port with some air cover was better than being at sea with no air cover (which disabuses the notion that “battleship admirals” just didn’t get it).
Because of the known deficiency in Army air defense (minimal antiaircraft artillery and many obsolete aircraft), Kimmel directed the ships in port maintain a higher status in aintiair readiness than they would normally have. Although the stories of ammunition being “locked up” (which was true for ships in repair status) have become common lore, a quarter of the fleet’s .50-caliber antiaircraft guns were manned and ready, and reacted almost immediately. The 5-inch guns came on line quickly, but too late to counter the torpedo bombers that led the first wave (which were most vulnerable to fire from the 5-inchers) and largely ineffective against the dive- and high-level bombers.
For every story of naval personnel being dumbfounded that they were are under attack, there are more in which naval personnel instantly grasped what was happening. The signal for air attack was being hoisted as the first bomb was falling on Ford Island, and most ships began responding almost immediately with the capability they had (although the gun crews were actually well-trained and drilled, the .50-caliber guns were just not particularly effective). The ships were more fully manned than they normally would have been: 70 percent of the officers and almost all enlisted were aboard ships in operational status. (Thanksgiving leave and liberty had been cancelled; Kimmel’s staff had been at work late Saturday—the fleet was not in “holiday routine.”) Of note, after Admiral Nimitz assumed command, he carefully reviewed Admiral Kimmel’s in-port air defense plan and chose not to change any of it, reasoning that it was as well-thought-out as could be given the system limitations.
Admiral Kimmel and his predecessor, Admiral James O. Richardson, were well aware that Pearl Harbor was vulnerable to air attack (contrary to popular lore). In at least four major fleet battle problems in the 1920s and 1930s (and numerous smaller exercises), U.S. carriers had “attacked” Pearl Harbor and had achieved surprise every time. Admiral Richardson was fired by President Roosevelt for vociferously arguing that putting the Pacific Fleet in Pearl Harbor was a provocation and a vulnerability rather than a deterrent to the Japanese, and that the base also lacked the support/supply infrastructure of the Pacific Fleet’s previous home ports of San Pedro and Long Beach in California.
The Pacific Fleet had deployed to Hawaii as part of an exercise in early 1940 and had been ordered by President Roosevelt to stay (imagine three carriers going out on RIMPAC and being directed to stay in Hawaii indefinitely, with no families or preparation and insufficient support infrastructure). When Kimmel assumed command, he lobbied continuously and vigorously for more long-range reconnaissance, more air-defense capability, and even barrage balloons and torpedo nets (although he eventually concurred that torpedo nets would be more trouble than they were worth). Almost none of what Kimmel requested was forthcoming due to the higher priority of the Atlantic or because the U.S. Navy didn’t have the respective capability yet.
The critical thing that Admiral Kimmel did not know (and no American knew) was that only at the 11th hour in late October had the Japanese figured out, through extensive trial and error, a torpedo fin configuration that would enable torpedoes to be launched from aircraft in water as shallow as Pearl Harbor. Kimmel anticipated a bomb threat that, barring a lucky hit like the one on Arizona, could damage a battleship, but wasn’t considered near as lethal as a torpedo. Kimmel also was not anticipating an attack of the scale of the one that actually occurred. In fact, the first time the Japanese ever launched a six-carrier strike was 7 December 1941—even they hadn’t practiced it.
Kimmel, along with everyone else in the U.S. Navy at the time, “mirror-imaged” Japanese capability in believing that their carriers would operate as ours, in single-carrier task groups. Many others woefully underestimated Japanese capability, e.g., since our torpedoes couldn’t be dropped in such shallow water, how could the Japanese with their “inferior” technology possibly do it?
Also contrary to lore, Kimmel and most other senior Navy leaders were very cognizant of the threat posed by carrier aviation. As early as 1916, the Navy General Board (the group of senior Navy admirals that advised the Secretary of the Navy—eventually supplanted by the OPNAV staff) stated that whoever controlled the air at sea had a decisive advantage.
During exercises in the 1930s, however, the carriers were always “sunk,” because they were highly vulnerable to the aircraft from the opposing carrier. The carriers were essentially viewed as a boxer with a knockout punch and a glass jaw, hence the continued focus on what the Navy viewed as a “balanced” fleet. Even the Japanese still viewed their battleships as the decisive force, even after the attack. Admiral Nagumo had a long list of reasons for not launching a third wave, but the primary one was that he did not know where the American carriers were and he assumed (erroneously) that we knew where he was, which made him feel acutely vulnerable to surprise attack by the American carriers.
The location of the Japanese carriers, particularly of the big fleet carriers, was the highest priority for U.S. naval intelligence in the Pacific in the year leading up to Pearl Harbor, and the organization had gone to 24/7/365 manning (normal now, but unheard of then) months before the attack in response to rising tensions. In the weeks before the attack, U.S. naval intelligence knew that we had lost track of the carriers, a fact of great concern, but something that had happened several times before for up to three weeks in the preceding year.
Although Japanese operations security (OPSEC) was not perfect, they did not make themselves an easy target to track—ever. Kimmel was so concerned about that lack of locating data on the carriers that he personally visited the basement location of Station Hypo (under the command of Commander Joe Rochefort, who worked for OP-20G in naval communications in Washington, not for Kimmel), which was also unheard of, to understand exactly which codes were being read, and how the traffic analysis process worked.
At the morning staff meeting on 2 December 1941, Kimmel said to Lieutenant Commander Edwin Layton, his fleet intelligence officer, words to the effect, “Do you mean to tell me the Japanese carriers could be rounding Diamond Head now and we wouldn’t know it?” Layton responded with, “Yes, but I would have hoped they would have been spotted by now.”
Two weeks prior the attack on Pearl Harbor, in response to rising tensions and even before the 27 November “War Warning” message, Kimmel directed the Pacific Fleet in Exercise 191. The exercise plan called for Lexington (acting as “Black Force”) to proceed 200 miles north of Oahu and launch a strike against “White Base” (Pearl Harbor) to test air defense reaction, and also to be on the lookout in case the Japanese might be in the area. The exercise was cut short by directive from Washington to avoid any actions that might be interpreted by the Japanese as provocative, as Washington had belatedly come to the conclusion that “buying time” was necessary. The air attack exercise scheduled for 29 November was cancelled.
Sources are in dispute as to whether Kimmel considered the north to be the primary threat sector, but this exercise (and the fact that previous exercise “surprise strikes” originated from the north due to the far less dense shipping traffic) suggests that he did. There is certainly strong evidence that the war planners on Kimmel’s staff viewed the north-northeast as the primary threat axis for a carrier air attack. As it turned out, the Japanese carrier force launched their strike from the same position as Lexington had been operating from only a couple of weeks earlier.
The United States had broken the primary Japanese diplomatic code (“Purple”) and some lesser diplomatic codes and was in the process of breaking the Japanese general naval operating code (then referred to as the “5 Num” code, and later retroactively as the JN-25 series). Sources conflict as to how much of the naval code the United States was reading before Pearl Harbor, but at best it wasn’t much. The real point is that neither Kimmel nor Layton had access to Purple (also known as “Magic”) intelligence, other diplomatic intercepts, or any JN-25 intelligence that might have existed.
Some of the “conspiracy” books about Pearl Harbor postulate that some sort of sinister intent on the part of Roosevelt was the reason Kimmel did not have access to this critical intelligence, but the reality appears to be pure bureaucratic buffoonery. Kimmel and Layton sensed that there was intelligence they were not getting (and General MacArthur and Admiral Hart in the Philippines were), especially after they got a couple Purple-derived messages by accident in July, and kept requesting to receive such intelligence. Admiral Stark, the CNO (and others of the very few who were cleared) assumed that Kimmel was getting Purple traffic, or was told erroneously that he was, and no one followed up to be sure. The Purple traffic was so tightly compartmented that no one actually had the big picture; the few senior leaders with access each sifted through hundreds of raw decoded intercepts, with no overall assessment.
Within the Purple traffic, and in the lesser diplomatic codes that were being decrypted very time-late, were plenty of indications that would have alerted Kimmel and Layton that Pearl Harbor was a target. They did not receive any of it. Prior to the attack on Pearl Harbor, there was a mountain of intelligence indicating that hostilities were imminent in the Far East between Japan and Britain, and probably the United States. In no message from Washington that Kimmel received, including the 27 November “War Warning,” was Pearl Harbor ever explicitly mentioned as a possible target. The fact that Washington was also directing that fighters be stripped from Hawaii, over Kimmel’s and Short’s protests, strongly suggested to Kimmel that Washington was not concerned about an attack on Pearl Harbor.
After the attack, the traditional American search for someone to blame (besides the Japanese) commenced in earnest. Secretary of the Navy Frank Knox arrived soon after the attack to investigate. The Army relieved General Short first, and in the spirit of “jointness” the Navy followed suit with Kimmel on 17 December 1941. Kimmel expected to be relieved and revert to his “permanent” rank of two-star rear admiral. (It was fairly common for three- and four-stars to accept follow-on positions at two-star rank. Rear Admiral Claude Bloch, the commander of the 14th Naval District [Hawaii] at the time of the attack, and who worked for both Kimmel and CNO Stark, had previously been the four-star commander-in-chief of the U.S. Fleet in 1938–40). Kimmel expected to be offered a follow-on job in which he could contribute to the war effort, but that never happened and he eventually reluctantly resigned.
The 1942 Roberts Commission, which was the first of numerous investigations of the Pearl Harbor attack, was conducted with none of the rules of evidence or rights of the accused (e.g., right to review evidence against them, etc.) of a court-martial. Nonetheless, it concluded that Kimmel and Short were guilty of “dereliction of duty,” resulting in a feeding frenzy by the press, public, and politicians. With no opportunity to appeal, Kimmel was accused of failure to conduct adequate long-range reconnaissance. This despite the fact that with acute shortages of aircraft, trained crews, and especially spare parts, Kimmel could only sustain a fraction of the coverage required. Moreover, the weather would have almost certainly prevented discovery of the Japanese anyway, even if Kimmel had been prescient enough to launch his few aircraft to the north on that particular morning.
On 7 December, there were 69 Navy long-range patrol aircraft (PBY-3 and PBY-5) on Oahu. Of these, only 15 had been on the island longer than six weeks. This number of patrol aircraft was nowhere near enough to provide 24-hour/360-degree coverage of Oahu. It was the position of the Roberts Commission (and many other historians later) that the inability to provide full coverage was no excuse for not searching the primary threat axis (north-northeast) and that there were enough aircraft to do so. This analysis generally fails to take into account the acute shortage of aircrew, the even more acute shortage of adequately trained aircrew, and a debilitating spare parts shortage—or weather.
PBY aircraft were on training flights out to 600 nautical miles north and west of Pearl Harbor on 4 and 5 December, but the weather on 6 December was not conducive to finding anything. In addition, fully aware of the likelihood of imminent war, neither Kimmel (nor Bloch) wanted to wear out his inadequate numbers of aircraft before the war started. If anything, Kimmel was guilty of being focused on executing the approved war plan (the latest in the Orange/Rainbow series), which was offensively oriented, upon the outbreak of hostilities.
Kimmel repeatedly requested a court-martial in order to defend himself, but was denied. The primary reason was that a trial would have risked exposing the code-breaking effort, which was considered (and really was) of paramount importance in winning the war. Another unstated reason is that a trial would have risked the reputations of many senior military and government officials in Washington, who were far more culpable of the failures that led to surprise at Pearl Harbor than Kimmel was.
If by this point you think that Admiral Kimmel was treated unfairly, you are in the company of admirals Zumwalt, Stockdale, Crowe, Hayward, Turner, Holloway, McKee, Lawrence, and 28 other three- or four-stars who signed a petition in 1991 to posthumously promote Rear Admiral Kimmel to Admiral. So far, it hasn’t happened.
Writing years after the war in 1965, Fleet Admiral Nimitz stated on a number of occasions that it was “God’s divine will” that Admiral Kimmel did not have the fleet at sea. Otherwise, “we could have lost ALL of our trained men . . . there would have been few trained men to form the nucleus of the crews for the new ships nearing completion.”
Of eight battleships at Pearl Harbor, only two were never returned to service:
  • Arizona (BB-39), sunk by magazine explosion, 1,177 killed (over 900 still aboard)
  • Oklahoma (BB-37), capsized (429 dead), raised, sold for scrap, lost at sea under tow
Three battleships were sunk, raised, and returned to the fleet:  
Three battleships were damaged and repaired, and returned to the fleet:  
West Virginia, Maryland, Tennessee, California, and Pennsylvania (plus Mississippi—BB-41), defeated a Japanese force at the Battle of Surigao Strait (part of the Battle of Leyte Gulf) on the night of 24–25 October 1944. Nevada shelled enemy shore defenses at Normandy (D-Day), in Southern France, and on Iwo Jima and Okinawa.
Of six light cruisers present, Raleigh (CL-7) and Helena (CL-50) were badly damaged. Helena returned to service in June 1942 and Raleigh that July. Honolulu (CL-48) was damaged and repaired by January 1942.
Of 30 destroyers, Cassin (DD-372), Downes (DD-375), and Shaw (DD-373) were heavily damaged, and Helm (DD-388) lightly damaged. For Cassin and Downes, machinery was salvaged, new hulls built, and they returned to service February 1944 and May 1943 respectively. Shaw was repaired by June 1942 and Helm by that January.
Other vessels:
  • Minelayer Oglala (CM-4) was sunk, raised, and repaired by February 1944
  • Target ship Utah (AG-16, ex-BB-31) capsized (64 dead); attempt to right failed
  • Repair ship Vestal (AR-4) was heavily damaged, beached, raised, and repaired by February 1942
  • Seaplane tender Curtiss (AV-4)was damaged and repaired by January 1942
  • Yard tug Sotoyomo (YT-9) was sunk, raised, and repaired by August 1942
  • Floating drydock YFD-2 was sunk, raised, and repaired by May 1942
I am not going to attempt to address the numerous conspiracy theories about Pearl Harbor (it is very much a cottage industry) other than to say that the vast majority are based on little to no actual evidence, usually taken out of context, and contain much speculation. What can be said is that U.S. political and military leaders knew full well that the economic sanctions were backing the Japanese into a corner and would almost certainly result in an outbreak of war, and that the outbreak was imminent. No one expected an attack on a scale as devastating as that at Pearl Harbor. Everyone grossly underestimated Japanese capability and resolve, assuming that when the expected war came, we would easily clean their clock.
It should also be noted that the Japanese made numerous errors of judgment as well and, but for some lucky breaks, the battle could have gone very differently. The accuracy of Japanese bombing was actually pretty abysmal, especially during the second attack wave when smoke, increased cloud cover, and antiaircraft fire prevented the dive-bombers from being able to conduct doctrinal dive-bombing (i.e., the dive-bombers couldn’t see the target from the altitude at which they would normally commence the dive, resulting in numerous misses. In fact, the very first bomb dropped in the first wave not only missed the seaplanes on the ramp at Ford Island, it also missed Ford Island, exploding in the mud off shore). Even among the 49 high-altitude bombers, which were relatively unmolested early in the battle, only about seven or eight bombs hit their targets on Battle Ship Row, with relatively little damage to the armored battleships except the one catastrophic hit on Arizona. In fact, it was the first dozen or so torpedo bombers that did the real killing, and the rest of the torpedoes were just overkill on Oklahoma and West Virginia.
One of the myths of Pearl Harbor is that the Japanese aviators were all battle-hardened veterans of the Sino-Japanese War. There were certainly some, but the reality is that the great majority of them were young green kids who, although exhaustively trained, were in combat for the first time. Comparing the number of aircraft involved to the number of hits actually achieved, the lack of combat experience shows. There is no substitute.
The many Japanese mistakes included the strike leader, Commander Mitsuo Fuchida, botching the signal to the strike force as to whether surprise had been achieved or not, and which plan (surprise or no surprise) to execute, which significantly affected timing and targets. Most important, the Japanese apparently had no plan to take out the repair facilities, submarine base, and fuel-storage facilities (all of which would play a critical role in their defeat) because most Japanese leaders believed the war would be too short for those to have an impact, and smoke from burning oil storage would just foul the range anyway. The Japanese, too, grossly underestimated their enemy.
Japanese losses were 29 aircraft with 55 personnel killed, and 5 midget submarines with 9 men killed and 1 captured.
Sources include: Air Raid: Pearl Harbor! Recollections of a Day of Infamy edited by Paul Stilwell, Naval Institute Press, 1981; Raising the Fleet: The Pearl Harbor Salvage Operation, 1941–1944 by Ernest Arroyo and Stan Cohen, Pictoral Histories, 2018; Pearl Harbor: Why, How, Fleet Salvage and Final Appraisal by Vice Admiral Homer N. Wallin, USN (Ret.), Naval History Division, 1968; Pearl Harbor: Warning and Decision by Roberta Wohlstetter, Stanford University Press, 1962; History of United States Naval Operations in World War II, Vol. III— Rising Sun in the Pacific by Rear Admiral Samuel Eliot Morison, USNR, Little Brown and Co., 1958; And I Was There: Pearl Harbor and Midway—Breaking the Secrets by Rear Admiral Edwin T. Layton, USN (Ret)., with Captain Roger Pineau, USNR (Ret). and John Costello, Konecky and Konecky, 1985; Sunday in Hell: Pearl Harbor Minute by Minute, by Bill McWilliams, Open Road Integrated Media, 2011; Pearl Harbor by H. P. Wilmott, Cassell & Co., 2001; Day of Deceit: The Truth About FDR and Pearl Harbor by Robert Stinnett, The Free Press, 2000; At Dawn We Slept: The Untold Story of Pearl Harbor, by Gordon Prange, Penguin Books, 1991.